The present invention relates generally to resonant power converters. More particularly, the present invention relates to gain enhancement techniques in resonant power converters through the use of auxiliary components and associated control circuitry.
Resonant converters (e.g., LLC converters) have become a popular topology in power conversion applications and can generally meet or exceed high efficiency requirements due to soft switching. However, achieving better performance (e.g., higher efficiency) is difficult because any combination of requirements for a holdup time, peak power, and wide input range regulation must be concurrently satisfied. In other words, any solution which may be provided to meet the requirements for holdup time, peak power, and/or wide regulation range, will generally have undesirable side effects with respect to the efficiency of the converter. As a consequence, the key parameters in resonant converters are designed to fashion a compromise between better performance and sufficient holdup time, peak power, and/or wide input range regulation.
Generally stated, a holdup time requirement for a converter is a minimum period of time for which a threshold power output must be maintained after, e.g., an input power failure.
As one example in the case of LLC converters, better efficiency may be obtained with larger magnetizing inductance in the power transformer because magnetizing current can accordingly be reduced. This is beneficial with respect to semiconductor conduction losses on the primary side of the transformer.
Alternatively, a longer holdup time can be realized with smaller magnetizing inductance in the power transformer according to the gain curve of the LLC converter. Eventually, the key parameters in the LLC converter are a compromise between high efficiency and a required minimum holdup time.
It would be desirable to provide a resonant converter design that supported higher efficiency by optimizing the key parameters (e.g., resonant parameters) of the resonant converter while further allowing for sufficient holdup time.